This invention relates to chain saw sharpening tools and more particularly to a hand-held guide for use in combination with a file for sharpening the chain saw cutting teeth.
Numerous devices, including hand-held devices, have been utilized in the prior art for aligning the position of a round or cylindrical file with with the cutting teeth of a chain saw blade in order to permit axial reciprocation of the file for sharpening the cutting edges of the teeth. Certain parameters and requirements are necessary for the accurate sharpening of such teeth, including an accurate depth adjustment of the cylindrical file within the tooth, and the capability of rotating the file periodically during use to assure the longest possible file life. These requirements have only been partially met in the prior art, particularly the depth of cut requirement, since the prior art fails to properly utilize the depth gage commonly incorporated as a part of the cutting teeth to stabilize the file and its guide during the cutting operation to insure a uniform and accurate cutting depth adjustment. Furthermore, prior art attempts to mount a file for easy rotation about its own axis in order to extend file life by permitting rotation of the file during use have not taken adequate precautions to assure that the placement of the file relative the guide is substantially uniform over the usable length of the file. Thus, the depth of cut in many cases varies along the axis of the file and an accurate, uniform sharpening of the cutting teeth is impossible.
In addition, the prior art does not provide an adequate gage for determining the proper height of the depth gage portion of chain saw teeth for permitting the accurate adjustment in this height required for proper sharpening.